[llvm] [NewPM][CodeGen] add TargetPassConfig like API (PR #70906)

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks commented:

initial review, I'll need to spend some more time understanding the current implementation of CodeGenPassBuilder; there are some things that don't seem very elegant at a cursory glance

https://github.com/llvm/llvm-project/pull/70906